proton (redirected from Proton pump)

proton, elementary particle having a single positive electrical charge and constituting the nucleus of the ordinary hydrogen atom. The positive charge of the nucleus of any atom is due to its protons. Every atomic nucleus contains one or more protons; the number of protons, called the atomic number, is different for every element (see periodic table). The mass of the proton is about 1,840 times the mass of the electron and slightly less than the mass of the neutron. The total number of nucleons, as protons and neutrons are collectively called, in any nucleus is the mass number of the nucleus. The existence of the nucleus was postulated by Ernest Rutherford in 1911 to explain his experiments on the scattering of alpha particles; in 1919 he discovered the proton as a product of the disintegration of the atomic nucleus. The proton and the neutron are regarded as two aspects or states of a single entity, the nucleon. The proton is the lightest of the baryon class of elementary particles. The proton and other baryons are composed of triplets of the elementary particle called the quark. A proton, for instance, consists of two quarks called up and one quark called down, a neutron consists of two down quarks and an up quark. The antiparticle of the proton, the antiproton, was discovered in 1955; it has the same mass as the proton but a unit negative charge and opposite magnetic moment. Protons are frequently used in a particle accelerator as either the bombarding (accelerated) particle, the target nucleus, or both. The possibility that the proton may have a finite lifetime has recently come under examination. If the proton does indeed decay into lighter products, however, it takes an extremely long time to do so; experimental evidence suggests that the proton has a lifetime of at least 10³¹ years.

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proton

Stable subatomic particle (one of the baryons) with a unit of positive electric charge and a mass 1,836 times that of the electron. Protons are found in the atomic nucleus along with neutrons. For every nucleus of a given element, the number of protons is always the same; this number is the element's atomic number. A single proton is the nucleus of an atom of ordinary hydrogen; as such, it is identical to the hydrogen ion (H⁺). Protons have antimatter counterparts (antiprotons), with the same mass but a negative charge. Protons are used as projectiles in particle accelerators to produce and study nuclear reactions. They are the chief constituent of primary cosmic rays and are among the products of radioactive decay (see radioactivity) and nuclear reactions.

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proton

a stable, positively charged elementary particle, found in atomic nuclei in numbers equal to the atomic number of the element. It is a baryon with a charge of 1.602176462 × 10^--19 coulomb, a rest mass of 1.672 62159 × 10^--27 kilogram, and spin ½

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Proton

A positively charged particle that is the nucleus of the lightest chemical element, hydrogen. The hydrogen atom consists of a proton as the nucleus, to which a single negatively charged electron is bound by an attractive electrical force (since opposite charges attract). The proton is about 1836 times heavier than the electron, so that the proton constitutes almost the entire mass of the hydrogen atom. Most of the interior of the atom is empty space, since the sizes of the proton and the electron are very small compared to the size of the atom. See Atomic structure and spectra

For chemical elements heavier than hydrogen, the nucleus can be thought of as a tightly bound system of Z protons and N neutrons. An electrically neutral atom will then have Z electrons bound comparatively loosely in orbits outside the nucleus. See Neutron, Nuclear structure

The numerical values of some overall properties of the proton can be summarized as follows: charge, 1.602 × 10^-19 coulomb; mass, 1.673 × 10^-27 kg; spin, (½)ℏ (where ℏ is Planck's constant h divided by 2&pgr;); magnetic dipole moment, 1.411 × 10^-26 joule/tesla; radius, about 10^-15 m. See Fundamental constants, Nuclear moments, Spin (quantum mechanics)

It is instructive to contrast the proton's properties with those of the electron. All of the electron's properties have been found to be those expected of a spin-½ particle which is described by the Dirac equation of quantum mechanics. Such a Dirac particle has no internal size or structure. See Electron, Relativistic quantum theory

By contrast, although it also has a spin of ½, the proton's magnetic moment, which is different from that for a Dirac particle, and its binding with neutrons into nuclei strongly suggest that it has some kind of internal structure, rather than being a point particle. Two different kinds of high-energy physics experiments have been used to study the internal structure of the proton. An example of the first type of experiment is the scattering of high-energy electrons, above say 1 GeV, from a target of protons. The angular pattern and energy distribution of the scattered electrons give direct information about the size and structure of the proton. The second type of high-energy experiment involves the production and study of excited states of the proton, often called baryonic resonances. It has been found that the spectrum of higher-mass states which are produced in high-energy collisions follows a definite pattern. See Baryon

In 1963, M. Gell-Mann and, independently, G. Zweig pointed out that this pattern is what would be expected if the proton were composed of three spin-½ particles, quarks, with two of the quarks (labeled u) each having a positive electric charge of magnitude equal to ⅔ of the electron's charge (e), and the other quark (labeled d) having a negative charge of magnitude of ⅓e. Subsequently, the fractionally charged quark concept was developed much further, and has become central to understanding every aspect of the behavior and structure of the proton. See Quarks

An important class of fundamental theories, called grand unification theories (GUTs), makes the prediction that the proton will decay. The predicted lifetime of the proton is very long, about 10³⁰ years or more—which is some 10²⁰ times longer than the age of the universe—but this predicted rate of proton decay may be detectable in practical experiments. See Grand unification theories

If the proton is observed to decay, this new interaction will also have profound consequences for understanding of cosmology. The very early times of the big bang (about 10^-30 s) are characterized by energies so high that the same grand unified interaction which would allow proton decay would also completely determine the subsequent evolution of the universe. This could then explain the remarkable astrophysical observation that the universe appears to contain only matter and not an equal amount of antimatter. See Elementary particle

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1.		PROTON - A home computer made by Acorn Computers under a contract won from the BBC in April 1981.
2.		PROTON - Something to do with Microsoft SoftLib?